Cusp Structures and

Magnetic Reconnection

at the Magnetopause

JACQUELINE JENSENUNIVERSITY OF CENTRAL FLORIDA

LASP BOULDER, CO

MENTOR: KARLHEINZ TRATTNER

Why Study Magnetic

Reconnection? Fundamental process

Sun: Solar Flares, CMEs, Flare Loops

Earth: Plasma Entry, Auroras, Magnetic storms

Ultimate Goal: Observe

magnetic reconnection in

situ through predictions of

reconnection site in model

Magnetic

Reconnection

The Magnetosphere

Solar wind: made up of plasma particles. Field distortion caused by pressure

Bow shock: shock wave before Earth’s magnetic field

Magnetosheath: region of higher density shocked plasma

Magnetopause: Boundary between the solar wind and Earth’s magnetic field

Cusp region: region with open field lines and direct solar wind access to upper atmosphere

Reconnection at the

Magnetopause

Plasma Entry

Precipitating cusp ions experience a velocity filter effect with lower

energies

convecting further poleward

Instrument Overview

Polar’s TIMAS Instrument

Mass spectrometer

Collects data on He+, He++, O+, and H+

Focused on H+ data

Measures 3D velocity

distributions

TIMAS Schematic

Southward IMF

Reconnection

Northward IMF

Reconnection

Southward IMF

Northward IMF

Not Just When, But

Where? Maximum Magnetic Shear Model

Predicts where reconnection is most likely to

occur

Correct 80% of the time

Shear angle plot:

Angle between solar wind magnetic field

and earth’s magnetic field lines

IMF clock angle:

Organizational

parameter for plots

Maximum Magnetic Shear

Magnetospheric Multiscale

Mission (MMS)

Anomalies

Observed: 176.1°

ACE: 112.5°

Observed: 153.5°

WIND: 132.8°

Observed: 50.3°

ACE: 80.0 °

Observed: 151.4°

ACE: 127.9°

Modeling the X-Line

• Ions are reflected when they

reach the ionosphere

• Xm = Distance to ionospheric

mirror point, calculated using

Tsyganenko 1996 model

(known value)

• Vm = cutoff velocity of

mirrored ions

• Ve = cutoff velocity of

earthward propagating ions

(precipitating)

• Xr = distance to reconnection

point (Calculated by program)

Modeling X-Line Part 2

• TIMAS data is

presented in a field-aligned coordinate system

• Gaussian distributions are fitted to the peaks

• Cutoff velocities are determined from Gaussian fits

Reconnection X-Line

Clock Angle 200-260

Anomalies arise between 200° and 260°

Occurs all year but predominately in spring time

Unknown why anomalies occur within this range

Data and Trends •58 events analyzed

•No events in main duration of winter

and summer

•Most events occurring in spring

Data and Trends

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total

Events 0 0 14 13 14 5 0 0 3 7 2 0 58

Above 0 0 9 5 0 0 0 0 0 1 0 0 15

Below 0 0 1 3 10 2 0 0 1 5 2 0 24

On Target

0 0 4 5 4 3 0 0 2 1 0 0 19

• 32.8% on target with model

• Predominately above in March

• Even statistics in April

• Predominately below after April

• Statistics for Bx value were

even

• Distribution of Clock Angles

was even

Conclusion

March events occur predominately above the

predicted x-line

April statistics are about even

All months after April seem to occur below the predicted x-line

April seems to be the turning point for this change

No other parameter yielded any trends

Future

Investigation

Plot more events

within this range

Does the pattern still occur?

Investigate other

Magnetopause parameters

Alfven Velocity

Plasma Beta

Questions?

Acknowledgements and

References

1. Trattner, K.J., S. A. Fuselier, and

S. M. Petrinec. “Location of the

reconnection line for northward

interplanetary magnetic field.”

J. Geophys. Res. 109 (2004)

This research was funded

by the National Science

Foundation under grand

number 1659878, as part

of a Research Experience

for Undergraduates at

the University of Colorado

at Boulder.

All pictures courtesy of

NASA. All plots and

spectrograms were

produced using an IDL

program written by

Karlheinz Trattner.